In my earlier Australian Patent Application No. 27199/84 there is disclosed a process and apparatus for forming an elongate concrete molded article from high slump concrete wherein surplus liquid is removed through a porous membrane extending around the outer perimeter of the article when the membrane is arranged to provide compression to the concrete within the mold and thereafter separating the membrane from the surface of the partially dried concrete and removing the article from the mold without significant damage to the cast concrete article. This enables almost immediate reuse of the mold.
A disadvantage of this method is that the external periphery of the concrete article, although visually undamaged, is not smooth. Furthermore, the process disclosed therein cannot be easily utilized by application of a membrane to the internal periphery of the article.